watchOS 5.1 (build 16R5577c) is an official Apple over-the-air update for the Apple Watch Series 3 (42mm, LTE), released on 2018-10-09T17:12:10Z. The update package is 555.17 MB. This is a delta (partial) update that requires 5.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d880527de169bdb00c1a85fbd1f0505975cdb2db.zip.